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SpaceX founder and CEO Elon Musk flew to Thailand this week to help rescue 13 people trapped inside a cave — and he brought along his latest invention to assist in the recovery effort.

Musk and his team of engineers at SpaceX and The Boring Co. designed and built a mini-submarine to help rescue a soccer team of 12 boys and their 25-year-old coach. They became trapped in the cave on June 23 when a flash flood blocked the entrance. After a long and dangerous rescue effort, the last members of the group were brought to safety today (July 10).

The rescue teams didn't end up using Musk's invention, which looks like a waterproof coffin. "The equipment they brought to help us is not practical [for use] with our mission," rescue operations commander Narongsak Osotthanakorn told the BBC. Nevertheless, Musk said he still sees a future for his spontaneous invention.

Named "Wild Boar" after the stranded youth soccer team, the mini-submarine arrived at the cave Monday morning (July 9). Only three days earlier, Musk announced on Twitter that he and his team of engineers from SpaceX and The Boring Co. were working to design the escape pod.

"I have one [of] the world's best engineering teams, who normally design spaceships and spacesuits, working on this thing 24 hours a day," Musk wrote in an email to Dick Stanton, one of the leaders of the search and rescue effort in Thailand, on July 8. "We are trying to get it right in a very short period of time." The Wild Boar began underwater tests in a swimming pool in Los Angeles on July 8, and Musk shipped the vessel to Thailand the next day.

Musk said the "kid-size submarine" uses part of a Falcon 9 rocket called a liquid oxygen transfer tube for the hull. It is too small for an average adult to fit inside, but a child or a small adult could have squeezed in there while divers carried the sub through the 2.5-mile-long (4 kilometers) cave system.

Without a passenger inside, the mini-submarine weighs about 90 lbs. (40 kilograms), which is "light enough to be carried by 2 divers, small enough to get through narrow gaps," Musk tweeted, adding that the contraption is "extremely robust." If rescue teams had maneuvered the tank through the underwater parts of the cave, they could have controlled buoyancy by adding or removing diver weight belts, Musk added. 

The Wild Boar is equipped with four air-tank connections, so up to four rescue divers can connect their hoses to share oxygen with the passenger.

This mini-submarine may not sound like the most practical or comfortable way to escape a flooded cave, but it's important to note that the trapped kids were not able to swim and had become weak from malnutrition and exhaustion, and none of them had any scuba diving experience, CNN reported. Musk's invention would have involved less physical effort from the kids being rescued. With that said, the capsule also looks like a claustrophobic's worst nightmare.

Musk tweeted that he was leaving the mini-submarine in Thailand "in case it may be useful in the future." So, what's next for the Wild Boar? The machine could be "good for rescuing vulnerable patients in dangerous environments, particularly if water, toxic gas or dangerous bacteria/viruses are present," Musk tweeted today (July 10). Two days earlier, Musk tweeted, "With some mods, this could also work as an escape pod in space." 

 

Email Hanneke Weitering at hweitering@space.com or follow her @hannekescience. Follow us @Spacedotcom, Facebook and Google+. Original article on Space.com.